Field
The present invention relates to a semiconductor device and a method for manufacturing the semiconductor device.
Description of Related Art
A technique that provides a PN junction diode as a protective element in combination with a vertical MOSFET has been known, with a view to enhancing the breakdown resistance of a semiconductor device. In this proposed technique, the PN junction diode serves as the protective element. It is accordingly preferable to form a PN junction diode including a thinner N− layer than an N− drift layer of the vertical MOSFET. JP 2005-520322A discloses a technique of reducing the thickness of an N− layer placed between electrodes forming a protective diode by removing part of the N− layer and forming a P-type layer in a removed location by regrowth.
In an application that employs a nitride semiconductor as the semiconductor, the inventors of the present application have found a problem with regard to the technique described in JP 2005-520322A that an unintended N-type carrier is generated at a regrowth interface to decrease the breakdown voltage of the PN junction diode. Other needs with regard to the prior art semiconductor device include downsizing, resource saving, easy manufacture, accuracy of manufacturing and improvement of workability.